Perhaps, the exos are part of the warminds controlled by Rasputin BUT because of either the Exos "deaths" or the destruction of the Warminds they are no longer linked. Even though they aren't connected to the Warminds any more the core principles of combat are programs and commands from the Warminds? The original Exos could have been built for maintenance but were then used by the warminds to actually combat the Darkness? If the Warminds were incapable of moving then maybe the Exo's were used as drones to actually fight? I could be wrong as I'm throwing this out there. Feel free to let me know what you all think.